Exhaust system

ABSTRACT

An exhaust system includes an exhaust gas-carrying pipe and a bypass to the exhaust gas-carrying pipe. The bypass has at least one inlet pipe and at least one outlet pipe. An exhaust gas sensor is arranged in the bypass between the inlet pipe and the outlet pipe in such a way that exhaust gas flowing through the bypass flows through the exhaust gas sensor. An accelerator accelerates the gas flow downstream of the exhaust gas sensor and is coupled to the outlet pipe. At least one inlet portion extends from the inlet pipe to the exhaust gas sensor, the flow cross-section of which is smaller than the flow cross-section of the inlet pipe and opens into an inlet of the exhaust gas sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. non-provisional application claiming the benefit of German Application No. 10 2021 122 492.6, filed on Aug. 31, 2021, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The disclosure relates to an exhaust system, in particular for a motor vehicle, a stationary engine, an engine of a ship, etc., having an internal combustion engine, having an exhaust gas-carrying pipe, and an exhaust gas sensor arranged in a bypass to the exhaust gas-carrying pipe.

BACKGROUND

Exhaust gas sensors are used to determine the amount of pollutants contained in an exhaust gas, for example the amount of carbon monoxide or nitrogen oxides. The determined amount of pollutant is in turn used to determine an amount of a reducing agent required for a selective catalytic reduction.

Exhaust gas sensors of this type are often arranged in a bypass outside of an exhaust gas-carrying pipe in order to prevent the sensor from overheating.

Due to the arrangement in a bypass, the flow rate at which the exhaust gas flows through the exhaust gas sensor is significantly reduced in comparison to the flow rate of the exhaust gas prevailing in the exhaust gas-carrying pipe.

However, in order to be able to determine an amount of pollutants contained in the exhaust gas as accurately as possible, it is necessary for the exhaust gas to flow through the exhaust gas sensor at a minimum flow rate. If the flow rate of the exhaust gas is below a minimum value, the measurement result will be delayed or recorded incorrectly. This problem occurs primarily when the engine is in an idle mode.

SUMMARY

The disclosure provides an exhaust system that allows the quickest and most accurate determination possible of a quantity of pollutants contained in the exhaust gas.

According to the disclosure, the exhaust system has an exhaust gas-carrying pipe and a bypass to the exhaust gas-carrying pipe. The bypass has at least one inlet pipe and at least one outlet pipe. An exhaust gas sensor is arranged in the bypass between the inlet pipe and the outlet pipe in such a way that the exhaust gas flowing through the bypass flows through the exhaust gas sensor. An accelerator accelerates the gas flow downstream of the exhaust gas sensor and is coupled to the outlet pipe. At least one inlet portion extends from the inlet pipe to the exhaust gas sensor, a flow cross-section of which is smaller than a flow cross-section of the inlet pipe and opens into an inlet of the exhaust gas sensor.

The exhaust system according to the disclosure has the advantage that, compared to conventional exhaust systems, an increased flow rate of the exhaust gas can be achieved through the exhaust gas sensor, on the one hand by way of the accelerator and on the other hand by the reduced flow cross-section of the inlet portion. In this way, the exhaust gas sensor can determine an amount of pollutants contained in the exhaust gas particularly accurately.

In particular, the flow rate at which the exhaust gas flows through the exhaust gas sensor is almost independent of a flow rate of the exhaust gas in the exhaust gas-carrying pipe. As a result, the exhaust gas sensor delivers particularly accurate measured values even when the engine is idling.

Due to the fact that the accelerator coupled to the outlet pipe accelerates the gas flow while the gas flow in the inlet pipe is not actively accelerated, an under-pressure is created at the outlet of the exhaust gas sensor. This under-pressure is used to actively draw the exhaust gas out of the inlet pipe, as a result of which the flow rate of the exhaust gas through the exhaust gas sensor is increased compared to a passive exhaust gas flow.

Because the inlet portion opens into the inlet of the exhaust gas sensor, a particularly short response time of the exhaust gas sensor is achieved.

A short response time and a precise measured value are required, in particular in a selective catalytic reduction, in order to calculate and inject a correct amount of urea at a certain point in time. In doing so, a high nitrogen oxide conversion rate can be achieved.

The exhaust gas sensor is, for example, a sensor for detecting nitrogen oxides.

The accelerator works in particular according to the principle of what is known as a jet pump, also referred to as a propellant pump. In such a pump, a pumping effect is generated by a fluid jet of a propellant medium, which sucks in, accelerates and conveys another medium through momentum exchange. Such an accelerator is particularly robust and requires little maintenance.

In particular, the exhaust system comprises a compressed gas source and the accelerator is fed with compressed gas from the compressed gas source.

According to one embodiment, the exhaust gas sensor is mounted in a housing, the bypass extending through the housing and the inlet portion being designed as a channel in the housing. This allows stable mounting of the exhaust gas sensor with a compact design at the same time.

In particular, the inlet pipe and the outlet pipe are connected to the housing in such a way that the bypass extends from the inlet pipe to the outlet pipe via the housing.

A receptacle for the exhaust gas sensor is preferably formed in the housing, an inner contour of the receptacle being adapted to an outer contour of the portion of the sensor accommodated in the housing.

The inner contour of the receptacle is preferably only slightly oversized in accordance with the dimensional tolerances of the exhaust gas sensor in order to ensure that the exhaust gas sensor can be easily inserted into the receptacle even if the tolerance is unfavorable.

Because the inner contour of the receptacle is adapted to an outer contour of the exhaust gas sensor, there is no gap, or only a small one, between the exhaust gas sensor and the receptacle. For example, there is a gap of at most 0.5 mm. As a result, exhaust gas cannot flow past the exhaust gas sensor, or only to a small extent. This also contributes to the fact that a quantity of pollutants contained in the exhaust gas can be determined particularly precisely by the exhaust gas sensor. In addition, stable mounting of the exhaust gas sensor on the housing is possible in this way.

The at least one inlet portion can overlap with the receptacle for the exhaust gas sensor and the inlet of the exhaust gas sensor can be arranged in the region of the overlap. An inlet opening is formed in the receptacle as a result of the overlap, without an additional recess being required next to the inlet portion. This contributes to a simple and compact construction of the exhaust system.

A connection for the compressed gas source is preferably present in the housing and the accelerator comprises a through-channel that extends through the housing from the connection, the outlet pipe adjoining the through-channel. Compressed gas can be blown into the through-channel and the outlet pipe from the compressed gas source, as a result of which the flow rate of the exhaust gas flowing through the through-channel and the outlet pipe is accelerated. The compressed gas source and the outlet pipe can be connected particularly easily in terms of flow due to the fastening to the housing and the existing through-channel.

An outlet portion, for example, is formed in the housing and opens into the through-channel. The outlet portion leads from an outlet of the exhaust gas sensor to the through-channel, such that the outlet of the exhaust gas sensor is fluidically connected to the through-channel and consequently also to the outlet pipe. When the accelerator is active, the increased flow rate in the outlet pipe creates an under-pressure in the outlet portion, actively drawing exhaust gas through the exhaust gas sensor.

Optionally, the through-channel tapers in portions toward the outlet pipe, with the outlet portion opening into the through-channel upstream of the taper. The taper also ensures improved acceleration.

The outlet portion extends parallel to the inlet portion, for example, at least in portions. This contributes to a compact construction of the exhaust system, in particular of the housing.

According to one embodiment, the housing is mounted on a plate whose base surface is larger than the base surface of the housing and that is used as a flange for fastening the housing to the exhaust system. The housing can be easily fastened to an exhaust system using the plate.

The inlet pipe and the outlet pipe can protrude into the exhaust gas-carrying pipe and an end portion of the inlet and outlet pipes, which end portion is arranged in the exhaust gas-carrying pipe, can in each case extend parallel to the exhaust gas-carrying pipe at least in portions. That is, the end portions of the inlet and outlet pipes are aligned in the flow direction of the exhaust gas. Thus, exhaust gas can flow directly from the exhaust gas-carrying pipe into the inlet pipe.

The end portion of the inlet pipe points in particular upstream and the end portion of the outlet pipe points in particular downstream. In other words, the inlet channel is preferably open in a direction opposite to a direction of flow of the exhaust gas and the outlet channel is open in particular in the direction of flow of the exhaust gas. In this way, a passive flow is conveyed through the bypass. More specifically, exhaust gas can flow into the bypass without deflection.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and features of the disclosure will become apparent from the following description and from the accompanying drawings, to which reference is made. In the drawings:

FIG. 1 shows an exhaust system according to the disclosure,

FIG. 2 shows a part of the exhaust system according to the disclosure from FIG. 1 ,

FIG. 3 is a detailed view of the exhaust system from FIG. 1 in the region of an exhaust gas sensor,

FIG. 4 shows a housing for accommodating an exhaust gas sensor, and

FIG. 5 is a side view of the housing from FIG. 4 .

DETAILED DESCRIPTION

FIG. 1 shows an exhaust system 10. The exhaust system 10 comprises an exhaust gas-carrying pipe 12 through which exhaust gas can flow from an internal combustion engine to an exhaust outlet.

The exhaust gas-carrying pipe 12 can be provided on its outside with insulation 13 at least in portions.

The exhaust system 10 comprises a bypass 14 to the exhaust gas-carrying pipe 12.

An exhaust gas sensor 16, in particular a nitrogen oxide sensor, is arranged in the bypass 14.

The bypass 14 has an inlet pipe 18 and an outlet pipe 20. It is also conceivable that two or more inlet pipes 18 or outlet pipes 20 are present.

The inlet pipe 18 and the outlet pipe 20 protrude into the exhaust gas-carrying pipe 12. An end portion 22, 24 of the inlet pipe 18 and outlet pipe 20, which end portion is arranged in the exhaust gas-carrying pipe 12, in each case extends parallel to the exhaust gas-carrying pipe 12 at least in portions.

The end portion 22 of the inlet pipe 18 points upstream, such that exhaust gas flowing through the exhaust gas-carrying pipe 12 can flow into the inlet pipe 18 without deflection.

The end portion 24 of the outlet pipe 20 points downstream. Exhaust gas flowing out of the outlet pipe 20 thus flows toward an exhaust gas outlet.

The exhaust gas sensor 16 is fluidically arranged between the inlet pipe 18 and the outlet pipe 20 in such a way that the exhaust gas flowing through the bypass 14 flows through the exhaust gas sensor 16.

In the figures, a flow path of the exhaust gas is illustrated using arrows.

The exhaust gas sensor 16 is mounted on a housing 26.

Furthermore, the inlet pipe 18 and the outlet pipe 20 are arranged on the housing 26. This can be seen in particular in FIG. 2 which shows part of the exhaust system 10.

That is, the bypass 14 extends through the housing 26.

The inlet pipe 18 and the outlet pipe 20 are, for example, welded to the housing 26 or otherwise fastened to the housing 26 in a suitable manner.

The housing 26 is mounted on a plate 27 whose base surface is larger than the base surface of the housing 26. The plate 27 is used as a flange for fastening the housing 26 to the exhaust system 10.

In the embodiment, the plate 27 is fastened to a flange 29 that is mounted on a pipe 31 arranged on the exhaust gas-carrying pipe 12.

FIG. 2 makes it clear how the housing 26 is designed on the inside. For this purpose, an outer wall of the housing 26 is shown transparently in FIG. 2 .

As can be seen in FIG. 2 , in the housing 26 there is a receptacle 28, i.e., a space, for the exhaust gas sensor 16, in which the exhaust gas sensor 16 is accommodated in portions.

In order to conduct as much as possible of the exhaust gas flowing through the bypass 14 through the exhaust gas sensor 16, the inner contour of the receptacle 28 is adapted to an outer contour of the portion of the exhaust gas sensor 16 accommodated in the housing 26.

In addition, an inlet portion 30 is formed in the housing 26 and extends from the inlet pipe 18 to the exhaust gas sensor 16. The inlet portion 30 is formed in particular by a channel in the housing 26.

In the embodiment, the inlet portion 30 is divided into two partial portions 32, 34, the two portions 32, 34 each opening into an inlet 36, 38 of the exhaust gas sensor 16. The position of the inlets 36, 38 of the exhaust gas sensor 16 is illustrated in FIG. 5 .

Both the part of the inlet portion 30 adjoining the inlet pipe 18 and the two partial portions 32, 34 have a smaller flow cross-section than the inlet pipe 18. Due to the reduced flow cross-section, a flow rate of the exhaust gas increases when it enters the inlet portion 30 or the partial portions 32, 34.

However, the flow cross-sections of the inlet portion 30 and of the two partial portions 32, 34 are large enough to prevent the inlet portion 30 and the partial portions 32, 34 from becoming clogged.

Due to the division into two partial portions 32, 34, different measuring regions of the exhaust gas sensor 16 can be subjected to a flow in a targeted manner, which contributes to a particularly fast and accurate measurement result.

Alternatively, it is also conceivable for two inlet pipes 18 to be present, a separate inlet portion extending from each inlet pipe 18 in the housing 26 to a respective inlet 36, 38 of the exhaust gas sensor 16. This embodiment is not shown in the figures for the sake of simplicity.

Alternatively, it is also conceivable, if the exhaust gas sensor 16 has only one inlet 36, for there to be only one inlet pipe 18 having a continuous inlet portion 30 adjoining the inlet pipe 18.

The two partial portions 32, 34 overlap with the receptacle 28 for the exhaust gas sensor 16. The partial portions 32, 34 are fluidically connected to the receptacle 28 as a result of the overlap. In other words, openings in the receptacle 28 are formed by the overlaps.

The inlets 36, 38 of the exhaust gas sensor 16 are arranged in the region of the overlaps, such that exhaust gas can flow from the partial portions 32, 34 of the inlet portion 30 into the exhaust gas sensor 16.

Furthermore, an outlet portion 40 is present in the housing 26.

The outlet portion 40 extends parallel to the partial portions 32, 34 of the inlet portion 30.

The outlet portion 40 is also formed by a channel in the housing 26.

The outlet portion 40 also overlaps with the receptacle 28, such that another opening is formed in the receptacle 28, an outlet 42 (see FIG. 4 ) of the exhaust gas sensor 16 being arranged in the region where the receptacle 28 overlaps with the outlet portion 40.

Preferably only one outlet portion 40 is provided as illustrated in the figures. This prevents recirculation of the exhaust gas in the receptacle 28, in particular in a gap between the outer contour of the exhaust gas sensor 16 and the inner contour of the housing 26.

An accelerator 44 is coupled to the outlet pipe 20 downstream of the exhaust gas sensor 16.

The accelerator 44 is coupled to a compressed gas source 46 that feeds compressed gas to the accelerator 44. The compressed gas source 46 is only shown schematically in FIG. 1 .

Air, for example, can be used as the compressed gas.

For example, the compressed gas source 46 generates compressed gas having an overpressure of 1 bar to 5 bar.

A flow rate of 10 m/s can be generated in the inlet portion 30, even at an overpressure of 1 bar.

The gas flow in the outlet pipe 20 can be accelerated by way of the accelerator 44.

With increasing overpressure, the flow rate can be further increased, but the consumption of compressed gas also increases. Thus, a balance must be struck between a desired flow rate and the most economical operation of the exhaust system 10.

A connection 48 for the compressed gas source 46 is present in the housing 26.

A connecting piece 50 is connected to the connection 48 and can be connected to a compressed gas line that leads to the compressed gas source 46.

The accelerator 44 comprises a through-channel 52 that extends through the housing 26 from the connection 48, the outlet pipe 20 adjoining the through-channel 52.

The gas flow in the outlet pipe 20 can be accelerated by way of the accelerator 44, in particular by compressed gas being blown into the through-channel 52.

Due to the acceleration, exhaust gas is entrained or sucked into the through-channel 52 in particular at the orifice of the outlet portion 40, as a result of which an under-pressure is produced in the outlet portion 40.

The under-pressure generated in the outlet portion 40 is used to increase the flow rate of the exhaust gas in the bypass 14, in particular when it flows through the exhaust gas sensor 16.

Optionally, the through-channel 52 tapers in portions toward the outlet pipe 20, preferably in a portion of the through-channel 52 directly adjoining the outlet pipe 20. This can be seen in FIG. 2 .

In this case, the outlet portion 40 opens into the through-channel 52 upstream of the taper 55.

FIG. 3 shows the exhaust system 10 in the region of the housing 26 in a further view. Also in FIG. 3 , the circumferential wall of the housing 26 is shown transparently.

It can be seen from FIGS. 2 and 3 that the outlet portion 40 laterally opens into the through-channel 52. This means that a longitudinal axis of the outlet portion 40 does not intersect the longitudinal axis of the through-channel 52, but rather extends slightly offset therefrom. As a result, an orifice 54 of the outlet portion 40 in the through-channel 52 is enlarged with the same diameter of the outlet portion 40 compared to an orifice when the longitudinal axis of the outlet portion 40 intersects the longitudinal axis of the through-channel 52.

A larger orifice has the advantage that the effect of the accelerator 44 is increased and more exhaust gas is entrained from the outlet portion 40.

The orifice 54 can be seen particularly clearly in FIG. 4 , which shows the housing 26, the hidden lines of the housing being shown for clarity.

The same also applies to the orifices of the partial portions 32, 34 in the receptacle 28, which can be seen in FIG. 5 .

In particular, the openings of the partial portions 32, 34 in the receptacle 28 have an oval shape, at least in portions.

FIG. 5 also shows the position of measuring regions 56, 58 of the exhaust gas sensor 16 using dashed lines. In particular, it can be seen from FIG. 5 that the openings of the partial portions 32, 34 in the receptacle 28 are arranged in the region of the inlets 36, 38 or the measuring regions 56, 58 of the exhaust gas sensor 16.

In addition, an outer contour of the exhaust gas sensor 16 is highlighted in FIG. 5 by a dashed line. This shows that the exhaust gas sensor 16 fits as precisely as possible in the receptacle 28 in such a way that a gap surrounding the exhaust gas sensor 16 is as small as possible and as little exhaust gas as possible can flow past the exhaust gas sensor 16 through the bypass 14.

The disclosure has been illustrated and described in detail in the drawings and the preceding description. This should be considered as illustrative and by way of example and not as limiting the disclosure to this description alone. Numerous other embodiments are possible. 

1. An exhaust system comprising: an exhaust gas-carrying pipe; a bypass to the exhaust gas-carrying pipe, the bypass having at least one inlet pipe and at least one outlet pipe; an exhaust gas sensor arranged in the bypass between the at least one inlet pipe and the at least one outlet pipe in such a way that exhaust gas flowing through the bypass flows through the exhaust gas sensor; an accelerator accelerates gas flow downstream of the exhaust gas sensor and is coupled to the outlet pipe; and at least one inlet portion extends from the at least one inlet pipe to the exhaust gas sensor, wherein a flow cross-section of the at least one inlet portion is smaller than a flow cross-section of the at least one inlet pipe and opens into an inlet of the exhaust gas sensor.
 2. The exhaust system according to claim 1, wherein the exhaust gas sensor is mounted in a housing, the bypass extending through the housing and the at least one inlet portion being formed as a channel in the housing.
 3. The exhaust system according to claim 2, including a receptacle for the exhaust gas sensor formed in the housing, an inner contour of the receptacle being adapted to an outer contour of a portion of the exhaust gas sensor accommodated in the housing.
 4. The exhaust system according to claim 3, wherein the at least one inlet portion overlaps with the receptacle for the exhaust gas sensor and the inlet of the exhaust gas sensor is arranged in a region of the overlap.
 5. The exhaust system according to any of claim 2, wherein the housing is mounted on a plate having a base surface that is larger than a base surface of the housing and that is used as a flange for fastening the housing to the exhaust system.
 6. The exhaust system according to claim 1, wherein the accelerator is fed with compressed gas from a compressed gas source.
 7. The exhaust system according to claim 6, including a connection for the compressed gas source in a housing for the exhaust gas sensor, and wherein the accelerator comprises a through-channel that extends through the housing from the connection, and with the at least one outlet pipe adjoining the through-channel.
 8. The exhaust system according to claim 7, wherein an outlet portion is formed in the housing and opens into the through-channel.
 9. The exhaust system according to claim 1, wherein the at least one inlet pipe and the at least one outlet pipe protrude into the exhaust gas-carrying pipe and an end portion of the at least one inlet and outlet pipes, which end portion is arranged in the exhaust gas-carrying pipe, in each case extends parallel to the exhaust gas-carrying pipe at least in portions.
 10. The exhaust system according to claim 9, wherein the end portion of the at least one inlet pipe faces upstream and the end portion of the at least one outlet pipe faces downstream.
 11. The exhaust system according to claim 8, wherein the outlet portion extends parallel to the at least one inlet portion at least in portions. 